The idea of virtuemart is very nice but the actual use of the system is far from "polished". Those that are interested in running anything serious will quickly find out they will end up having to pay for some custom programming or spend long hours customizing the functions yourself.
Support for the program has been in decline since I started to use the program and is now non existent. However, visiting the forum and asking for help you are sure to find programmers eager to do custom work for you for a price.
There also seems not to be much forward momentum in keeping the product up to date with whats available on the market. By the time you're done paying for custom modules, programming, or templates you may as well buy a commercial product.